Cannot start virtualbox VM's: Kernel driver is not installed

I'm a Linux Novice

Was running 12.04 with virtualbox 4.2. Everything was rosie.

Upgraded to 12.10; now Virtualbox will run, but can start any VM's. Get error 'kernel driver not installed' I've ran /etc/init.d/vboxdrv setup but get error 'Your kernel headers for kernel 3.8.0-32-generic cannot be found'

I tried running apt-get linux-headers-3.8.0-32-generic but get error 'Pakcage linux-headers-3.8.0.32-generic is not available, but is referred to by another package'.

uname -r responds with 3.8.0-32-generic

ls /usr/src contains linux-headers-3.5.0-42; linux-headers-3.5.0-42-generic & vboxhost-4.3.0

How do I resolve this? I now understand I should have installed DKMS before performing the OS upgrade and kernel headers would have been updated.